Benchmark: for...in vs map - MeasureThat.net

Tests:

for...in
const obj = { a: 'a', b: 'b', c: 'c', d: 'd', e: 'e', f: 'f' } const mapped = [] for (const key in obj) { mapped.push({ key: key, val: obj[key] }) }
map
const obj = { a: 'a', b: 'b', c: 'c', d: 'd', e: 'e', f: 'f' } const mapped = Object.keys(obj).map((key) => ({ key: key, val: obj[key] }))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for...in
map

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

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Let's break down the benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark is comparing two approaches to iterate over an object: `for...in` and `map`. The goal is to determine which approach is faster.

**Options Compared**

Two options are being compared:

1. **For...in**: This method uses a loop with the `for...in` statement, which iterates over the properties of an object. In this case, the loop iterates over the keys of the `obj` object and pushes them into the `mapped` array along with their corresponding values.
2. **Map**: This method uses the `map()` function, which applies a provided function to each element of an array-like or iterable object. In this case, it uses `Object.keys(obj)` to get an array of keys from the `obj` object and then maps over that array to create a new array with key-value pairs.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **For...in**:
	+ Pros: Simple, easy to read, doesn't require the use of additional libraries or functions.
	+ Cons: Can be slower than `map` because it uses a loop, which is generally less efficient than array methods like `map`.
* **Map**:
	+ Pros: More concise, often faster because it leverages the optimized implementation of the `map()` function.
	+ Cons: Requires understanding of array methods and can be less readable for some developers.

**Library/Function Used**

In this benchmark, the `Object.keys(obj)` function is used to get an array of keys from the `obj` object. This is a built-in JavaScript function that returns an array of strings representing the property names of an object.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in these benchmarks beyond what's already mentioned (e.g., using `map()` and `for...in`). The focus is on comparing two common iteration approaches.

**Other Alternatives**

If you're looking for alternative ways to iterate over an object, here are a few options:

* **Using `forEach()`**: Instead of `map()`, you can use the `forEach()` function to iterate over the keys of an object.
* **Using a `for` loop with index**: You can also use a traditional `for` loop with an index variable to iterate over the properties of an object.
* **Using `reduce()`**: Depending on your specific use case, you might consider using the `reduce()` function to accumulate values from an array or iterable.

Keep in mind that these alternatives may have different performance characteristics and trade-offs compared to `map()` and `for...in`.

Related benchmarks:

for...in vs map (version: 0)

Comparing performance of: for...in vs map

Created: 2 years ago by: Guest

Jump to the latest result

for...in

map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):